One method for rapidly deploying an object from a moving craft is to allow the deployed object to fall freely away from the moving craft under the influence of drag until the object reaches the correct deployment distance At that point, the deployment of the towline connecting the craft to the object should stop abruptly so that the object immediately accelerates to the moving craft's speed. The resulting high tension on the towline, however, would usually cause it to break. To avoid such breakage, brake systems have been used to slow the rate of deployment before the object reaches the correct deployment distance and thereby reduce or eliminate the sudden tension increase that would otherwise occur.
Early brake-control systems were often arranged to enable a human operator to control the deployment rate manually and thereby bring the speed of the object with respect to the craft below the level that results in breakage In one example of this type of system, a brake engaged automatically when the relative object speed fell below a threshold. Nonetheless, such systems depended on the skill of the operator to achieve the fastest possible towline deployment without towline breakage.
More-recent systems have deployed brakes automatically in response to deployment distance. One such system prevents the deployment rate from exceeding a predetermined limit, and, when the object reaches a preset distance, it engages a brake system to slow the object to a stop at the desired deployment distance. Although such systems eliminate the need for human control, their use of fixed deployment speed and brake-engagement distance prevents them from deploying these objects in minimum times for all craft speeds.